HSC Survey Results

German Bank Survey # 5 Results from 29/09/2024

Survey Details

6 commercial purse seiners conducted this fishing survey on 29/09/2024 starting at 20:00:00.

All vessels ran two transects in the German Bank box and two transect in the Seal Island Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

There were large plankton clouds which have affected this estimate. This estimate may be more conservative due to editing processes taking this into account. There will be more uncertainty regarding this estimate until a review is completed.

Preliminary biomass prediction for German Bank using standardized parallel transects is 10,596mt, and with turnover applied 5,068mt. The preliminary biomass estimate for Seal Island is 3,135mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-09-29 19:22:47 2024-09-29 21:46:53 -66.400 43.565 -66.401 43.234 GB 36.90 8.30
BP T02 2024-09-29 22:26:00 2024-09-30 00:45:25 -66.261 43.236 -66.264 43.565 GB 36.59 8.50
BP T03 2024-09-30 01:11:02 2024-09-30 02:59:25 -66.193 43.504 -66.193 43.247 GB 28.69 8.58
BP T04 2024-09-30 03:13:18 2024-09-30 05:03:46 -66.149 43.248 -66.150 43.504 GB 28.55 8.37
FM T01 2024-09-29 20:36:27 2024-09-29 23:02:37 -66.448 43.565 -66.447 43.234 GB 37.67 8.35
FM T02 2024-09-29 23:41:52 2024-09-30 02:03:20 -66.308 43.234 -66.310 43.568 GB 37.83 8.66
FM T03 2024-09-30 02:35:08 2024-09-30 04:23:42 -66.211 43.502 -66.211 43.245 GB 29.24 8.72
FM T04 2024-09-30 04:40:13 2024-09-30 06:27:18 -66.151 43.249 -66.154 43.502 GB 28.90 8.74
LB T01 2024-09-29 19:32:23 2024-09-29 22:09:47 -66.425 43.566 -66.424 43.234 GB 38.16 7.85
LB T02 2024-09-29 22:52:27 2024-09-30 01:20:01 -66.286 43.233 -66.286 43.567 GB 37.99 8.34
LB T03 2024-09-30 01:51:01 2024-09-30 03:33:54 -66.203 43.504 -66.201 43.248 GB 29.17 9.18
LB T04 2024-09-30 03:51:03 2024-09-30 05:43:14 -66.144 43.246 -66.146 43.504 GB 29.40 8.49
LJ T01 2024-09-29 19:35:12 2024-09-29 22:04:08 -66.378 43.569 -66.378 43.234 GB 37.25 8.10
LJ T02 2024-09-29 22:43:13 2024-09-30 01:07:52 -66.241 43.233 -66.241 43.566 GB 37.03 8.29
LJ T03 2024-09-30 01:31:54 2024-09-30 03:18:00 -66.182 43.502 -66.183 43.248 GB 28.27 8.63
LJ T04 2024-09-30 03:33:10 2024-09-30 05:27:01 -66.125 43.247 -66.125 43.502 GB 28.41 8.08
LM T01 2024-09-29 19:21:09 2024-09-29 21:43:38 -66.493 43.567 -66.493 43.233 GB 37.87 8.61
LM T02 2024-09-29 22:16:35 2024-09-30 00:36:31 -66.356 43.234 -66.355 43.566 GB 37.53 8.69
LM T03 2024-09-30 01:10:43 2024-09-30 02:54:31 -66.231 43.502 -66.231 43.247 GB 28.89 9.02
LM T04 2024-09-30 03:08:45 2024-09-30 05:00:15 -66.174 43.245 -66.174 43.503 GB 29.28 8.51
MS T01 2024-09-29 19:21:19 2024-09-29 22:07:42 -66.470 43.567 -66.470 43.234 GB 40.66 7.92
MS T02 2024-09-29 22:49:01 2024-09-30 01:06:54 -66.331 43.236 -66.331 43.568 GB 38.73 9.10
MS T03 2024-09-30 01:44:12 2024-09-30 03:26:35 -66.220 43.502 -66.221 43.247 GB 30.05 9.51
MS T04 2024-09-30 03:43:13 2024-09-30 05:36:58 -66.164 43.247 -66.163 43.501 GB 30.02 8.55

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LM T02 -35.5 -49.483 0.040
LB T01 -35.5 -49.878 0.036
LM T04 -35.5 -53.377 0.016
LJ T03 -35.5 -53.942 0.014
LJ T04 -35.5 -54.075 0.014
LJ T01 -35.5 -54.387 0.013
BP T04 -35.5 -54.412 0.013
FM T04 -35.5 -54.728 0.012
FM T02 -35.5 -54.803 0.012
FM T03 -35.5 -55.199 0.011
LM T03 -35.5 -55.218 0.011
LB T02 -35.5 -55.502 0.010
LJ T02 -35.5 -55.807 0.009
LB T03 -35.5 -55.834 0.009
MS T04 -35.5 -55.990 0.009
LB T04 -35.5 -56.040 0.009
BP T03 -35.5 -56.253 0.008
FM T01 -35.5 -56.936 0.007
MS T02 -35.5 -57.285 0.007
BP T01 -35.5 -57.707 0.006
BP T02 -35.5 -57.742 0.006
MS T03 -35.5 -58.209 0.005
MS T01 -35.5 -59.172 0.004
LM T01 -35.5 -59.811 0.004
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 826.1781 -54.4195 0.0129 10,595.586 74.2 77.2 2,909.85 27.46
Seal Island -35.5 287.0035 -55.1170 0.0110 3,134.639 25.8 22.8 252.86 8.07

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by LB, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by LM, at the following location:

Annual Summaries

This table does not include the biomass from adhoc surveys.

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2024-08-04 12,233 12,233 2023-08-06 2,687 2,687 2,021 2,021
Seal Island 1 2024-08-04 45,930 NA 2023-08-06 1,205 NA 929 NA
German Bank 2 2024-08-18 14,054 11,668 2023-08-20 4,930 4,406 3,282 2,887
Seal Island 2 2024-08-18 6,285 NA 2023-08-20 1,918 NA 897 NA
German Bank 3 2024-09-02 15,499 12,639 2023-09-03 9,959 8,901 8,372 7,660
Seal Island 3 2024-09-02 3,770 NA 2023-09-03 2,063 NA 1,099 NA
German Bank 4 2024-09-15 24,824 21,033 2023-09-13 16,266 13,203 15,011 12,498
Seal Island 4 2024-09-15 1,369 NA 2023-09-13 5,636 NA 4,045 NA
German Bank 5 2024-09-29 10,595 5,068 2023-09-27 15,242 11,360 13,503 9,978
Seal Island 5 2024-09-29 3,134 NA 2023-09-27 53,844 NA 42,269 NA
German Bank 6 NA NA NA 2023-10-11 23,614 20,057 26,563 23,390
Seal Island 6 NA NA NA 2023-10-11 15,261 NA 14,381 NA
German Bank 7 NA NA NA 2023-10-24 11,184 5,502 13,033 6,803
Seal Island 7 NA NA NA 2023-10-24 1,006 NA 1,087 NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 German Bank 83,882 66,116 81,785 65,237
2023 Seal Island 80,933 NA 64,707 NA
2024 German Bank 77,205 62,641 NA NA
2024 Seal Island 60,488 NA NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number GB2024-07 GB2024-08
Ground GB GB
Date 29/09/2024 29/09/2024
Wind Direction (km/h) W W
Swell (m) 0.5 0.5
Air Temp (c) 13 13
Tow Details
Tow Start 18:55:00 19:10:00
Tow End 19:05:00 19:20:00
Start Lat 43.57017 43.56633
End Lat 43.56583 43.57117
Start Lon -66.35767 -66.35867
End Lon -66.35633 -66.36650
Avg Tow Depth (m) 1.262619 7.195101
Speed 1.7 2.4
Heading 163 310
Tide Direction against with
Other Data Collection
Flow Start 931518 964610
Flow End 964610 980257
No. Revolutions 33092 15647
Distance (m) 889.2813 420.4818
Volume 2793.677 1320.944
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2024-07, which was against the tide and had an average depth of 1.2626186m. The second tow is GB2024-08, which was with the tide and had an average depth of 7.195101m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.55. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

The speed for each transect are rudimentary and are calculated based on distance. If a significant amount of distance is cut, the speed will appear slower.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.